I don't see how MC would gry Along with Stark. So I think more of going to Tywin and rebuild Castamere as new Blackstone lands. for side in war I would say loyalist to moment of Rhegar death then switch said to Tywin.
Just go with what you feel will be good bro. New strory and events are better for me personally because it keeps story fresh and unpredictable for reader. I personally made story with terible writing but story I quaiet good I guess maybe you will find some ideas. :)